Coal has often been described as one of the most difficult materials to sample because of its inherent heterogeneity. Therefore, fundamental to any coal assessment is an understanding of the impacts of the geological heterogeneity on coal quality variability for a given area. Since the mid-1970s, the U.S. Geological Survey (USGS) has maintained a coal quality database of national scope named USCHEM, which currently contains data for over 13,000 samples. A subset of the USCHEM database called COALQUAL Version 1.3 was initially published in 1994. Version 3.0 of the COALQUAL database represents a major editing effort to resolve some of the DOS software limitations used by earlier versions of the database. Because of database size limits during the development of COALQUAL Version 1.3, many analyses of individual bench samples were merged into whole coal bed averages. The methodology for making these composite intervals was not consistent. Size limits also restricted the amount of georeferencing information and forced removal of qualifier notations such as "less than detection limit" (<) information, which can cause problems in using the data. A review of the original data sheets revealed that COALQUAL Version 2.0 was missing information, which was needed for a complete understanding of a coal section. Another important database issue to resolve was the USGS "remnant moisture" problem. Prior to 1998, tests for remnant moisture (as-determined moisture in the sample at the time of analysis) were not performed on any USGS major, minor, or trace-element coal analyses. Without the remnant moisture, it is impossible to convert the analyses to a usable basis (as-received, dry, etc.). Based on remnant moisture analyses of hundreds of samples of different ranks and known residual moisture reported (moisture reported at the time of the ultimate and proximate analysis) after 1998, it was possible to develop a method to provide reasonable estimates of remnant moisture for older data to make it more useful in COALQUAL Version 3.0. In addition, the COALQUAL Version 3.0 database is improved by (1) adding qualifiers, including statistical programming to deal with the qualifiers; (2) clarifying the sample compositing problems; and (3) adding associated samples (discussed in more detail in report). Version 3.0 of COALQUAL also represents the first attempt to incorporate data verification by mathematically crosschecking certain analytical parameters. Finally, a new database system was designed and implemented to replace the outdated DOS program used in earlier versions of the database. The COALQUAL Version 3.0 database is located at http://ncrdspublic.er.usgs.gov/coalqual/. Parameter name Description Ash Softening Ash softening temperature in degrees Fahrenheit as determined by ASTM method D1857 in reducing atmosphere (ASTM, 2014). This parameter was ASHSOF in COALQUAL Version 1.3 and Version 2.0. *Ash Softening Q* Qualifier for Ash Softening. Ash Fluid Ash fluid temperature in degrees Fahrenheit as determined by ASTM method D1857 in re...

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A review of publicly available coal quality data during the coal resource assessment of the southwestern part of the Powder River Basin, Wyoming (SWPRB), revealed significant problems and limitations with those data. Subsequent citations of data from original sources often omitted important information, such as moisture integrity and information needed to evaluate the issue of representativeness. Occasionally, only selected data were quoted, and some data were misquoted. Therefore, it was important to try to resolve issues concerning both the accuracy and representativeness of each available dataset. The review processes demonstrated why it is always preferable to research and evaluate the circumstances regarding the sampling and analytical methodology from the original data sources when evaluating coal quality information, particularly if only limited data are available. Use of the available published data at face value would have significantly overestimated the coal quality for all the coal fields from both the Fort Union and Wasatch Formations in the SWPRB assessment area. However, by using the sampling and analytical information from the original reports, it was possible to make reasonable adjustments to reported data to derive more realistic estimates of coal quality.

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